Effect of L-carnitine administration on the modulated rat brain protein concentration, acetylcholinesterase, Na+K+-ATPase and Mg2+-ATPase activities induced by forced swimming.

BACKGROUND: Forced exercise produces free radicals and L-carnitine (L-C) administration reduces oxidative stress. AIM: To investigate whether short (2 hours) or prolonged (3 hours) forced swimming could modulate total antioxidant status (TAS), protein concentration and activities of acetylcholinesterase (AChE), Na(+)K(+)-ATPase and Mg(2+)-ATPase in rat brain following intraperitonal administration of L-C (300 mg/kg). METHODS: TAS, protein and enzyme activities were measured spectrophotometrically. RESULTS: TAS, protein concentration and AChE activity were reduced, whereas Na(+)K(+)-ATPase and Mg(2+)-ATPase were significantly increased after either 2 or 3 hours of training. L-C administration resulted in a profound restoration of TAS and protein concentration whereas AChE and Na(+)K(+)-ATPase were increased before exercise, followed by AChE restoration and Na(+)K(+)-ATPase reduction after exercise. Mg(2+)-ATPase remained unchanged. An in vitro study using L-C incubation of brain homogenates previously treated with L-C resulted in complete restoration of the modulated enzymes, whereas the enzyme activities from untreated animals remained unaltered. CONCLUSIONS: Short or prolonged swimming in rats may result in a reduction of brain TAS, protein concentration and AChE activity, and an activation of Na(+)K(+)-ATPase and Mg(2+)-ATPase. L-C administration may prevent reduction in TAS and protein concentration, and a decrease in AChE and Na(+)K(+)-ATPase activity; the latter reached pre-exercise values after L-C incubation.

Serum paraoxonase/arylesterase activities in phenylketonuric patients on diet.

AIM: To compare serum paraoxonase/arylesterase (PON-aryl) activities in phenylketonuric (PKU) patients with high and low phenylalanine (Phe) blood concentration. PATIENTS AND METHODS: Seventeen poorly controlled PKU children (off diet) underwent clinical and laboratory examinations before and after 30 days adhering to their special diet (on diet), whereas controls (N=24) were examined once. Lipid, lipoprotein levels and paraoxonase (PON 1) activities were measured with the Bayer Advia 1650 Clinical Chemistry System. Apolipoprotein AI (Apo AI) levels were determined by the Dade Behring BN ProSpec nephelometer, whereas total antioxidant capacity (TAC), PON-aryl and Phe levels were measured spectrophotometrically. RESULTS: Phe significantly differed among the groups. Lipids and lipoproteins, except high-density-lipoprotein-cholesterol (HDL-C) and Apo AI, were higher when off diet than those on diet. HDL-C and Apo AI were similar in patients and controls. TAC (0.99+/-0.19 mmol/l) was significantly lower when the patients were off diet than when they adhered to diet and controls (1.71+/-0.20 and 1.81+/-0.20 mmol/l P<0.001 respectively). PON 1 and PON-aryl activities (68+/-2 U/min/ml, 88+/-26 KU (min/ml) in children with high Phe were reduced as compared with those with low blood Phe levels (152+/-41 U/min/ml, 107+/-23 KU/min/ml P<0.001) and controls (146+/-43 U/min/ml, 109+/-41 KU/min/ml P<0.001). The enzyme activities positively correlated with HDL-C and Apo AI when PKU patients were on diet and controls as well as with TAC in all the groups, whereas negatively correlated with Phe levels. CONCLUSIONS: PON-aryl activities are strongly related to the dietary control of PKU patients.

The effect of L-cysteine and glutathione on inhibition of Na+, K+-ATPase activity by aspartame metabolites in human erythrocyte membrane.

BACKGROUND: Reports have implicated Aspartame (N-L-a-aspartyl-L-phenylalanine methyl ester, ASP) in neurological problems. AIM: To evaluate Na(+), K(+)-ATPase activities in human erythrocyte membranes after incubation with the ASP metabolites, phenylalanine (Phe), methanol (MeOH) and aspartic acid (Asp). METHODS: Erythrocyte membranes were obtained from 12 healthy individuals and were incubated at 37 degrees C for 1 h with the sum or each of the ASP metabolites separately, which are commonly measured in blood after ASP ingestion. Na(+), K(+)-ATPase and Mg(2+)-ATPase activities were measured spectrophotometrically. RESULTS: Membrane Mg(2+)-ATPase activity was not altered. The sum of ASP metabolite concentrations corresponding to 34, 150 or 200 mg/kg of the sweetener ingestion resulted in an inhibition of the membrane Na(+), K(+)-ATPase by -30, -40, -48%, respectively. MeOH concentrations of 0.14, 0.60 or 0.80 mM decreased the enzyme activity by -25, -38, -43%, respectively. Asp concentrations of 2.80, 7.60 or 10.0 mM inhibited membrane Na(+), K(+)-ATPase by -26, -40, -46%, respectively. Phe concentrations of 0.14, 0.35 or 0.50 mM reduced the enzyme activity by -24, -44, -48%, respectively. Preincubation with L-cysteine or reduced glutathione (GSH) completely or partially restored the inhibited membrane Na(+), K(+)-ATPase activity by high or toxic ASP metabolite concentrations. CONCLUSIONS: Low concentrations of ASP metabolites had no effect on Na(+), K(+)-ATPase activity. High or abuse concentrations of ASP hydrolysis products significantly decreased the membrane enzyme activity, which was completely or partially prevented by L-cysteine or reduced GSH.

The effect of MTHFR(C677T) genotype on plasma homocysteine concentrations in healthy children is influenced by gender.

OBJECTIVE: To explore the influence of gender, together with folate status, on the relation between the common methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism and plasma total homocysteine (tHcy) concentrations in healthy children. DESIGN: Cross-sectional study by face-to-face interview. SETTING AND SUBJECTS: A total of 186 sixth-grade students participated from twelve randomly selected primary schools in Volos, Greece. METHODS: Fasting tHcy, folate, and vitamin B(12) were measured in plasma. The MTHFR genotypes were determined. Anthropometric and dietary intake data by 24-h recall were collected. RESULTS: Geometric means for plasma tHcy, plasma folate and energy-adjusted dietary folate did not differ between females and males. The homozygous mutant TT genotype was associated with higher tHcy only in children with lower plasma folate concentrations (<19.9 nmol/l, P = 0.012). As a significant gender interaction was observed (P = 0.050), we stratified the lower plasma folate group by gender and found that the association between the genotype and tHcy was restricted to males (P = 0.026). Similar results were obtained when folate status was based on estimated dietary folate. Specifically, only TT males that reported lower dietary folate consumption (<37 microg/MJ/day) had tHcy that was significantly higher than tHcy levels of C-allele carriers (P = 0.001). CONCLUSIONS: Under conditions of lower folate status (as estimated by either plasma concentration or reported dietary consumption), gender modifies the association of the MTHFR(C677T) polymorphism with tHcy concentrations in healthy children. SPONSORSHIP: Kellog Europe.

Raised beta-endorphin serum levels in children with atopic dermatitis and pruritus.

Atopic dermatitis (AD) is a pruritic cutaneous inflammatory condition. As pruritus and pain are very close symptoms, we determined the beta-endorphin serum concentrations in 21 atopic children with pruritus (group A) and 20 children with healed AD without pruritus (group B). Twenty-five healthy school children were the control group. The beta-endorphin serum concentrations (14.95 +/- 2.75 pmol/l) in group A were statistically (P < 0.001) elevated in our patients compared to controls (8.85 +/- 2.39 pmol/l) whereas these in group B were not elevated (9.4 +/- 2.46 pmol/l). We suggest that the elevated beta-endorphin concentrations in atopic patients with pruritus confirm the hypothesis that there is an increased activity of their opioid system and that an opioid antagonist might block itching which is their major clinical symptom.

Protective effect of L-phenylalanine on rat brain acetylcholinesterase inhibition induced by free radicals.

OBJECTIVE: To investigate whether the preincubation of brain homogenates with L-phenylalanine (Phe) could reverse the free radical effects on brain acetylcholinesterase (AChE) activity, since it has been reported that Phe binds hydroxyl radicals ((*)OH). DESIGN AND METHODS: Two well established systems were used for production of free radicals: (a) FeSO(4) (84 microM) plus ascorbic acid (400 microM), and (b) FeSO(4), ascorbic acid and H(2)O(2) (1 mM) at 37 degrees C in homogenates of adult rat whole brain. Changes in brain AChE activity were studied in the presence of each system separately. RESULTS: AChE was inhibited (18-28%) by both systems of free radicals. This inhibition was reversed when the brain homogenate was preincubated with Phe 1.8 mM. CONCLUSIONS: In accordance with our previous reports, Phe could protect against the direct action of (*)OH radicals on brain AChE and in this way it might be useful in the prevention of certain cholinergic neural dysfunctions.

Maternal--neonatal serum selenium and copper levels in Greeks and Albanians.

AIM: To evaluate selenium (Se) and copper (Cu) concentrations in Greek and Albanian immigrant mothers and in the cord blood of their newborns. SUBJECTS AND METHODS: From 1118 Greek and 820 Albanian mothers and from the cord blood of their neonates blood was obtained for Se and Cu measurement. Se and Cu concentrations were determined in sera with graphite furnace atomic absorption spectroscopy (GFAAAS) and atomic absorption spectrometry, respectively. In all, 30 days' nutrient intakes were evaluated in both groups. RESULTS: Animal protein, Se and Cu intakes were poor in the Albanians vs the Greeks (P < 0.001). Se concentrations in the Greek mothers (68.3 +/- 8.5 microg/l) and in their newborns (37.02 +/- 8.9 microg/l) were found higher as compared with those in Albanian mothers (37.4 +/- 9.9 microg/l) and in their newborns (34.3 +/- 9.1 microg/l) (P < 0.001). Cu levels were also found higher (P < 0.001) in the Greek mothers (1687 +/- 353 microg/l) and in their neonates (449 +/- 87 microg/l) compared with those in the Albanian mothers (959 +/- 318 microg/l) and in their newborns (229 +/- 67 microg/l). Additionally, 31.5% of neonates born to Albanian women with Se concentrations less than 28 microg/l had higher Se levels (P < 0.01) than their mothers. CONCLUSIONS: The low Se and Cu levels evaluated in the Albanian mothers and their newborns could be related to their poor animal protein intake which could be the consequence of their low socioeconomic status. As an effective preventive measure, accurate dietetic strategies to assess the requirements of pregnant immigrant women for trace elements may be planned in Greece.

Effect of diet on plasma total antioxidant status in phenylketonuric patients.

BACKGROUND: Phenylketonuria (PKU), an inborn error of phenylalanine (Phe) metabolism, is treated with a low Phe lifelong diet, which is a vegetarian and contains many antioxidants. AIM: The aim of this study was to evaluate the effect of diet on plasma total antioxidant status in our PKU patients. METHODS, RESULTS: Twenty-two PKU patients on strict diet (group A), 24 PKU patients who did not accurately follow their dietary control (group B) and 40 healthy children (controls) of comparable age took part in this study. Nutrients, as well as blood levels of lipids, vitamin C, beta-carotene and alpha-tocopherol were evaluated in all groups. Vitamin C intake and its blood levels did not differ between the groups. However, the intake of beta-carotene, alpha-tocopherol (2211+/-116, 14+/-1.0 mg/24 h) and their blood levels (0.7+/-0.09, 34+/-0.9 micro mol/l) in group A were statistically significantly higher (P<0.001) as compared with those of group B (1352+/-118, 10+/-1.0 mg/24 h and 0.49+/-0.08, 22+/-0.6 micromol/l) and controls (1290+/-120, 9.0+/-0.9 mg/24 h and 0.40+/-0.09, 24+/-1.6 micromol/l). Lipid intakes and their blood levels were lower in patients on the strict diet. Plasma total antioxidant status was higher in the same group of patients (group A). Additionally, positive correlations were found between the antioxidant vitamin blood levels and the plasma total antioxidant status in the groups, especially in the group A. PKU patients of group A showed significantly higher antioxidant status (1.6+/-0.2 mmol/l) as compared with those of group B (1.0+/-0.19 mmol/l; P<0.001) and controls (1.01+/-0.2 mmol/l). CONCLUSIONS: The high plasma antioxidant status in patients with PKU, especially in those with a good compliance with their diet, is possibly due to the amounts of antioxidants which are present in their special low Phe vegetarian diet.

Glucose-6-phosphate dehydrogenase deficiency neonatal screening: preliminary evidence that a high percentage of partially deficient female neonates are missed during routine screening.

OBJECTIVES: To provide preliminary evidence that the currently employed semiquantitative method of screening for glucose-6-phosphate dehydrogenase (G6PD) deficiency can only detect infants who are totally deficient for G6PD and misses all cases of partial G6PD deficiency. SETTING: General population: 2150 randomly selected blood samples from the Blood Donation Department, Speliopouleion General Hospital, Athens, Greece. Neonate population: 2000 samples from neonates (50% male; 50% female) in maternity hospitals in the greater Athens area. High risk population: a total of 545 individuals from 133 families in the Athens area, the minimum acceptance criteria being the parents and any brother or sister. METHOD: Blood specimens from neonates or adults were collected and either spotted and dried on special filter paper (Schleicher and Schull 2992, Darmstadt, Germany) or used in tubes after being heparinised. For the quantitative evaluation of G6PD enzyme activity, the Quantase G6PD screening kit (Quantase Limited, Perth, UK) was used. Quantase G6PD controls (Quantase Limited) were used at three levels of G6PD. These controls are rated at 24, 30, and 37 degrees C. Alternatively, we used the Sigma G6PDH controls (Sigma Chemical Company, St Louis, USA) which are rated at 30 and 37 degrees C. The assay was performed according to the instructions included in the kit with the modification for haemoglobin normalisation. RESULTS: General population: 36 females who were classified as having normal enzymatic activity with the semiquantitative test, were classified as partially deficient with the quantitative test. Neonate population: using the quantitative test, the percentage of G6PD deficient neonates in this population was 5.5%, compared with 3.17% reported in routine screening using the semiquantitative method. High risk population: the quantitative method detected 28 cases of total or partial G6PD deficiency in sisters of males with known total deficiency. The semiquantitative CONCLUSIONS: A considerable amount of partially G6PD deficient female neonates (heterozygotes) are undetected and classified as having normal enzymatic activity using the semiquantitative method, which uses a cut off of 2.1 U/g haemoglobin (Hb). The use of a fully quantitative G6PD screening kit is proposed, employing the automated haemoglobin normalisation and a cut off of 6.4 U/g Hb. Any neonate with an activity below this mark should be regarded as G6PD deficient, and all preventive measures should be taken.

The effect of galactose metabolic disorders on rat brain acetylcholinesterase activity.

To evaluate whether in classical galactosemia galactose (Gal), galactose-1-phosphate (Gal-1-P) and galactitol (Galtol) affect brain acetylcholinesterase (AChE) activity, various concentrations (1-16 mM) of these compounds were preincubated with brain homogenates of suckling rats as well as with pure eel Electroforus electricus AChE at 37 degrees C for 1 h. Initially, Galtol (up to 2.0 mM) increased (25%) AChE activity which decreased. thereafter, reaching the control value in high Galtol concentrations. Gal-1-P decreased gradually the enzyme activity reaching a plateau (38%), when incubated with 8-16 mM. However, when the usually found 2 mM of Galtol and 2 mM of Gal-1-P, concentrations in galactosemia were added in the incubation mixture simultaneously, brain AChE was stimulated (16%). Galtol or Gal-1-P modulated brain AChE as well as enzyme activity of E.electricus in the same way. Gal, Glucose (Glu) and glucose-1-phosphate (Glu-1-P) had no effect on AChE activity. It is suggested that Galtol as well as Gal-1-P can affect acetylcholine degradation acting directly on AChE molecule. Consequently the direct action of these substances on the enzyme might explain the brain cholinergic dysfunction in untreated galactosemia patients.

L-phenylalanine effect on rat diaphragm acetylcholinesterase and Na+,K(+)-ATPase.

The effect of different L-phenylalanine (Phe) concentrations (0.24-12.1 mM), on acetylcholinesterase (AChE) and Na+,K(+)-ATPase activities of diaphragm homogenates from 21-day old rats and pure enzymes, was investigated at 37 degrees C. AChE and Na+,K(+)-ATPase activities were determined after preincubation with Phe. AChE activity in diaphragm homogenate or in pure eel E. electricus enzyme showed a decrease, which reached a maximum of 18% with Phe concentrations of 0.9-12.1 mM. However lower Phe concentrations (0.24 mM) increased the enzyme activity (by approximately 22%), only in the diaphragm homogenate. Diaphragm-associated Na+,K(+)-ATPase activity showed a progressive and concentration-dependent decrease, by about 30-35% in the presence of high Phe concentrations. Pure enzyme activity (from porcine cerebral cortex) was not affected by high Phe concentrations (> 0.48 mM), while it was increased by low concentrations. The above results suggest: a) A direct inactivating effect of high Phe concentrations on AChE and an indirect activating effect induced by low concentrations. b) A direct activating effect of low Phe concentrations and an indirect inactivating effect of high ones on Na+,K(+)-ATPase. c) The combination of high Phe concentrations effects on AChE and Na+,K(+)-ATPase could influence the levels of the diaphragm synaptic ACh.

In vitro influence of phenylalanine on acetylcholinesterase activity and DNA.

Acetylcholinesterase (AChE) is a significant component of the membrane contributing to the permeability changes during synaptic transmission and conduction. Phenylketonuria is a group of metabolic disorders in which phenylalanine (Phe) is highly elevated in blood (up to 0.1 M) resulting in mental retardation etc. AChE activity was measured spectrophotometrically after incubation with various Phe concentrations. Phe interaction with DNA was evaluated with an established HPLC method. Phe was found to inhibit AChE almost 40%, at a concentration of 5 mM, whereas a 62.5% DNA peak exclusion (molecular interaction) was observed when Phe was incubated with DNA at a concentration of 3 mM. In addition the ratio of DNA: Phe determined the potency of the observed molecular effect.

Reduced Mg2+-ATPase activity in the hypoglycemic adult rat brain.

The effects of different a-D-Glucose (Glu) concentrations (0-16 mM) on Na+, K+-ATPase and Mg2+-ATPase activities were investigated in homogenates of adult male rat whole brain at 37 degrees C. The enzyme activities were determined after 1 h preincubation with Glu. Brain Na+, K+-ATPase was not affected by Glu different concentrations. On the contrary, Mg2+-ATPase activity was considerably reduced with Glu concentrations lower than 4 mM. The enzyme was inhibited 40%, 50% or 80% with 3, 2 or 1 mM of Glu, respectively. The above results suggest: a) The various concentrations of Glu have no effect on brain Na+, K+-ATPase activity. b) The inhibited brain Mg2+-ATPase in hypoglycemia produces low intracellular Mg2+, which could modulate the activity of Mg2+-dependent enzymes and the rates of protein synthesis and growth of the cell.

Protective effect of L-cysteine and glutathione on rat brain Na+,K+-ATPase inhibition induced by free radicals.

The aim of this study was to investigate whether the preincubation of brain homogenates with L-phenylalanine (Phe), L-cysteine (Cys) or reduced glutathione (GSH) could reverse the free radical effects on Na+,K+-ATPase activity. Two well established systems were used for the production of free radicals: 1) FeSO4 (84 microM) plus ascorbic acid (400 microM) and 2) FeSO4, ascorbic acid and H2O2 (1 mM) for 10 min at 37 degrees C in homogenates of adult rat whole brain. Changes in brain Na+,K+-ATPase activity and total antioxidant status (TAS) were studied in the presence of each system separately, with or without Phe, Cys or GSH. TAS value reflects the amount of free radicals and the capacity of the antioxidant enzymes to limit the free radicals in the homogenate. Na+,K+-ATPase was inhibited by 35-50% and TAS value was decreased by 50-60% by both systems of free radical production. The enzymatic inhibition was completely reversed and TAS value increased by 150-180% when brain homogenates were preincubated with 0.83 mM Cys or GSH. However, this Na+,K+-ATPase inhibition was not affected by 1.80 mM Phe, which produced a 45-50% increase in TAS value. It is suggested that the antioxidant action of Cys and GSH may be due to the binding of free radicals to sulfhydryl groups of the molecule, so that free radicals cannot induce Na+,K+-ATPase inhibition. Moreover, Cys and GSH could regulate towards normal values the neural excitability and metabolic energy production, which may be disturbed by free radical action on Na+,K+-ATPase.

L-phenylalanine effect on rat brain acetylcholinesterase and Na+,K(+)-ATPase.

The effect of different L-phenylalanine (Phe) concentrations (0.1-12.1 mM), on acetylcholinesterase (AChE) and Na+,K(+)-ATPase activities of brain homogenate and pure enzymes, was investigated at 37 degrees C. AChE and Na+,K(+)-ATPase activities were determined according to Ellman G. L., Courtney D., Andres V. and Featherstone R. M. (1961), Biochem. Pharmacol. 7, 88-95 and Bowler K. and Tirri R. (1974), J. Neurochem. 23, 611-613) respectively, after preincubation with Phe. AChE activity in brain homogenate or in pure eel E.electricus enzyme showed a decrease, which reached up to 18% with concentrations of 0.9-12.1 mM. Brain homogenate Na+,K(+)-ATPase activity showed an increase 16-65% with 0.24-0.9 mM of Phe, while an activity increase of 60-65% appeared with 0.9-12.1 mM of Phe. Pure enzyme activity (from porcine cerebral cortex) was not affected by high Phe concentrations, while it was increased by low concentrations. The above results suggest: a) A direct effect of Phe on AChE, b) A direct effect of low Phe concentrations and an indirect effect of high ones on Na+,K(+)-ATPase.

Persistent coagulopathy during Escherichia coli sepsis in a previously healthy infant revealed undiagnosed tyrosinaemia type 1.

Hereditary tyrosinaemia type 1 (HT1) is caused by an enzymatic defect in tyrosine metabolism. It is an autosomal recessive disorder and affects both sexes equally. In young infants HT1 can present as severe liver involvement and in older infants as liver failure and renal tubular dysfunction together with growth failure and rickets. The authors report the case of a 5-month-old, previously healthy, male infant who presented with Escherichia coli sepsis and severe coagulopathy due to liver dysfunction. Despite the early diagnosis of HT1 and treatment with 2-(2-nitro-4-trifluoromethylbenzoyl)-1, 3-cyclohexanedione (NTBC), the patient died from severe coagulopathy and multi-organ failure.

Alpha-tocopherol supplementation prevents the exercise-induced reduction of serum paraoxonase 1/arylesterase activities in healthy individuals.

OBJECTIVE: To investigate PON 1/Aryl activities in basketball players with or without alpha-T supplementation pre- and post-training. Vitamin E (alpha-tocopherol, alpha-T) reduces lipid peroxidation. Paraoxonase 1/arylesterase (PON 1/Aryl) activities are closely related to oxidation and atherogenesis. SUBJECT/METHODS: Blood was obtained from 10 players pre- (group A), post-exercise (group B) and after 1 month on alpha-T (200 mg per 24 h orally) supplementation pre- (group C) and post-exercise (group D). Lactate, pyruvate, muscle enzyme activities, creatine kinase, lactate dehydrogenase and total antioxidant status (TAS) were measured with commercial kits. Catecholamines and alpha-T were determined with high-performance liquid chromatography methods and PON 1/Aryl activities spectrophotometrically. RESULTS: Lactate, pyruvate, muscle enzyme activities and catecholamines were increased (P<0.001) in all groups post-training. Alpha-T levels remained unaltered pre- vs post-exercise. TAS was decreased in all the groups post training. PON 1/Aryl activities were significantly decreased post-exercise (group B) (PON1: 65+/-12 U min(-1) ml(-1), Aryl: 58+/-14 KU min(-1) ml(-1)) as compared to those pre-exercise (group A) (PON1: 142+/-16 U min(-1) ml(-1), Aryl: 114+/-12 KU min(-1) ml(-1), P<0.001). In contrast, the studied enzyme activities remained practically unaltered after alpha-T supplementation pre- vs post-training. Both enzyme activities positively correlated to TAS (r=0.60, P<0.001). CONCLUSIONS: Alpha-T supplementation may result in protection of the enzyme PON 1/Aryl activities from free radical production.

Dramatic reduction of erythrocyte glucose-6-phosphate dehydrogenase activity in athletes participating in the ultradistance foot race "Spartathlon".

OBJECTIVE: To investigate the effect of a long-distance endurance exercise "Spartathlon" on erythrocyte glucose-6-phosphate dehydrogenase (G(6)PD) activity. MATERIAL AND METHODS: The study comprised 15 male runners, median age 36.5 years. Blood samples were obtained in the 15 min before the race and again within 15 min after the end of the race. Erythrocyte glutathione (GSH and GSSG) and plasma malonyldialdehyde were measured with HPLC methods, and total antioxidant capacity (TAC), total hyperoxides and G(6)PD activity with commercial kits. Lipids, uric acid and total bilirubin were determined with a clinical chemistry analyser. RESULTS: Total hyperoxides were found statistically reduced, whereas total bilirubin was measured elevated post-race. Interestingly, GSSG levels were found increased (167.3+/-12.0 versus 219.5+/-20.3 micromol/L; p<0.005) as well as GSSG/GSH ratio (16.0+/-1.3 versus 20.60+/-1.65; p<0.05) post-race. In contrast, G(6)PD activity was found remarkably decreased (8.72+/-3.10 versus 3.8+/-2.5 U/g Hb; p<0.0001) pre versus post the event. CONCLUSION: Red blood cell G(6)PD activity in athletes may be reduced post-race as a consequence of the modulation of NADP/NADPH levels and elevation of the erythrocyte GSSG, and especially GSSG/GSH ratio, resulting in an impairment of the hexose monophosphate shunt.